Figure 1.

Probability distribution functions (PDFs) for gaps and call durations. (a) PDFs for inter-call times (gaps), ${\tau }_{ij}$ and PDFs for the average gaps, (${\langle \tau \rangle }_{ij}$ - calculated with respect to individual pairs ij). The pairs (ijs) are chosen irrespective of the age and gender of the individuals in the pair. The green up-triangles and blue down-triangles correspond to $\mathcal{U}$ (set of all frequent contacts). The red circles and the orange squares correspond to $\mathcal{S}$ (set of regular contacts). (b) PDFs for call durations, $T_{ij}$ and for the average call durations, (${\langle T\rangle }_{ij}$). The different symbols are used in the same sense as in (a).